HEBRON  The most immediate deadline set by the new airline security bill is to screen all bags by the middle of next month, but it's not the toughest.

According to those involved in the process and outside observers, the most difficult task for the new federal Transportation Security Agency is to install bomb-screening machines at all airports by the end of next year.

Installing explosive detection systems by Dec. 31, 2002, is probably the biggest challenge we currently face, especially with the state of manufacturing, said Hank Price, spokesman for the federal Transportation Department, which is overseeing creation of the new agency.

Cincinnati/Northern Kentucky International Airport does not have one of the $1 million machines, which scan bags moving on a conveyor belt for explosives.

Mr. Price says there are 153 machines now in use nationwide, but he would not say where. He also says to cover every one of the nation's 453 commercial airports will require more than 2,000 machines.

The problem is that only two companies are certified to make the machines; and, at top production, the two firms can make about 12 a month apiece.

We're looking at a minimum of two years before all the machines are in place and fully functional, said Rick Charles, a former airline executive and now the head of the aviation program at Georgia State University in Atlanta.

Mr. Price, the Transportation Department spokesman, would not say how many machines Cincinnati would need, or when the local airport might get one.

During a visit to Cincinnati in October, Jane Garvey, head of the Federal Aviation Administration, said the local airport is a great candidate for a machine, and said the production schedule needed to be improved.

But she did not give any indication when Cincinnati  a Category B airport, or less of a security risk than such locations as Los Angeles, Miami or New York  would receive a machine.

Mr. Price did say the capacity of each machine is about 250 bags an hour. In 2000, Cincinnati airlines handled nearly 34 million bags, an average of more than 3,800 an hour based on a 24-hour day (although commercial passenger flights do not operate locally between midnight and 5 a.m.)

It is unknown whether bags scanned elsewhere  those originating in another city, but passing through the Delta hub here as passengers connect to other flights  would need to be scanned here. Neither airline officials nor Mr. Price would comment on this question.

And it's a key question, because Cincinnati is the second-largest hub for Delta Air Lines. Only 29 percent of all passengers at the local airport begin or end a trip here, which equates to about 1,100 bags an hour, again based upon a 24-hour day.

The new federal security agency will operate the machines, taking over the function from airlines and their contractors.

The security agency also will pay for the machines through funding from Congress, transferred security funds from the FAA and a new $2.50 passenger fee for each leg of a trip, which begins next month.

In addition to getting enough machines, other obstacles remain.

The machines can be as long as a football field, and many airports don't have enough room.

This could be a problem in Cincinnati as well, because Delta's local baggage handling system runs through an underground tunnel from the terminal to the airline's two concourses and onto the concourse of regional subsidiary Comair.